I had a similar experience getting my K60 rear to seat. Mine just took time for the bead to seat. I too put about 50psi in it and with lots of lube, left it about half an hour or so and bit by bit it seated itself. The lesson I learned was to be patient with it rather than keep on deflating and re inflating. As long as it is close to being seated and well lubed, it will seat, eventually.